scholarly journals Miniaturization of a Koch-Type Fractal Antenna for Wi-Fi Applications

2020 ◽  
Vol 4 (2) ◽  
pp. 25 ◽  
Author(s):  
Dmitrii Tumakov ◽  
Dmitry Chikrin ◽  
Petr Kokunin
Keyword(s):  
Reflection Coefficient ◽  
Fractal Antenna ◽  
Wire Length ◽  
Dipole Antennas ◽  
Central Vertex ◽  
Type Curve ◽  
Base Frequency ◽  
First Order ◽  
Small Antennas ◽  
Linear Dimensions

Koch-type wire dipole antennas are considered herein. In the case of a first-order prefractal, such antennas differ from a Koch-type dipole by the position of the central vertex of the dipole arm. Earlier, we investigated the dependence of the base frequency for different antenna scales for an arm in the form of a first-order prefractal. In this paper, dipoles for second-order prefractals are considered. The dependence of the base frequency and the reflection coefficient on the dipole wire length and scale is analyzed. It is shown that it is possible to distinguish a family of antennas operating at a given (identical) base frequency. The same length of a Koch-type curve can be obtained with different coordinates of the central vertex. This allows for obtaining numerous antennas with various scales and geometries of the arm. An algorithm for obtaining small antennas for Wi-Fi applications is proposed. Two antennas were obtained: an antenna with the smallest linear dimensions and a minimum antenna for a given reflection coefficient.

FIRST ORDER RAMAN SCATTERING FROM SEMICONDUCTOR QUANTUM DOTS

1989 ◽  
Vol 03 (08) ◽  
pp. 1167-1181 ◽  
Author(s):  
P.A.M. RODRIGUES ◽  
HILDA A. CERDEIRA ◽  
F. CERDEIRA
Keyword(s):  
Crystal Structure ◽  
Quantum Dots ◽  
Raman Spectrum ◽  
Raman Scattering ◽  
Bulk Material ◽  
Semiconductor Quantum Dots ◽  
Polycrystalline Materials ◽  
Nanometer Size ◽  
First Order ◽  
Linear Dimensions

We develop a model appropriate for describing the Raman spectrum of samples, containing a collection of semiconductor quantum dots with and without dispersion in their linear dimensions. These nanometer size crystallites are assumed to have the same atomic arrangement as that of the bulk material and to be embedded in a host material made up of a different semiconductor of the same crystal structure. The results from our calculations are compared to previous models for polycrystalline materials.

Design Tri-Band Fractal Antenna with Minkowski Island Split Ring Resonator Structures

2015 ◽  
Vol 781 ◽  
pp. 73-76 ◽  
Author(s):  
H. Nornikman ◽  
Muhammad Ramlee Kamarudin ◽  
Badrul Hisham Ahmad ◽  
Mohamad Zoinol Abidin Abd Aziz
Keyword(s):  
Reflection Coefficient ◽  
Patch Antenna ◽  
Ring Resonator ◽  
Split Ring Resonator ◽  
Fractal Antenna ◽  
Optimal Result ◽  
Split Ring ◽  
Resonant Frequencies ◽  
Cst Microwave Studio

The paper investigates the effect of Minkowski Island split ring resonator (MI-SRR) on the microstrip fractal patch antenna. Firstly, a basic Minkowski Island had been simulated in the CST Microwave Studio. Then, the addition of several sizes of the Minkowski Island split ring resonator on the substrate had been generated tri-band resonant frequencies. The optimal result of this tri-band antenna 2.394 GHz, 3.528 GHz and 5.257 GHz with a gain of 0.874 dB, 1.41 dB and 2.94 dB and the reflection coefficient magnitudes of - 21.945 dB, - 17.154 dB and – 16.536 dB. The reflection coefficient magnitudes of the simulation and fabricated antenna also had been compared. The target application for this antenna is for WLAN and WiMAX.

scholarly journals Scattering of interface wave by bottom undulations in the presence of thin submerged vertical wall with a gap

2016 ◽  
Vol 21 (2) ◽  
pp. 303-322
Author(s):  
P. Dolai
Keyword(s):  
Reflection Coefficient ◽  
Vertical Wall ◽  
Finite Depth ◽  
Zero Order ◽  
Wave Number ◽  
Reflection Coefficients ◽  
First Order ◽  
Interface Wave ◽  
Lower Fluid ◽  
Order Reflection

AbstractIn this paper, the problem of interface wave scattering by bottom undulations in the presence of a thin submerged vertical wall with a gap is investigated. The thin vertical wall with a gap is submerged in a lower fluid of finite depth with bottom undulations and the upper fluid is of infinite height separated by a common interface. In the method of solution, we use a simplified perturbation analysis and suitable applications of Green’s integral theorem in the two fluid regions produce first-order reflection and transmission coefficients in terms of integrals involving the shape function describing the bottom undulations and solution of the scattering problem involving a submerged vertical wall present in the lower fluid of uniform finite depth. For sinusoidal bottom undulations, the first-order transmission coefficient vanishes identically. The corresponding first-order reflection coefficient is computed numerically by solving the zero-order reflection coefficient and a suitable application of multi-term Galerkin approximations. The numerical results of the zero-order and first-order reflection coefficients are depicted graphically against the wave number in a number of figures. An oscillatory nature is observed of first-order reflection coefficient due to multiple interactions of the incident wave with bottom undulations, the edges of the submerged wall and the interface. The first-order reflection coefficient has a peak value for some particular value of the ratio of the incident wavelength and the bottom wavelength. The presence of the upper fluid has some significant effect on the reflection coefficients.

scholarly journals Scattering of water waves by a submerged nearly circular cylinder

1995 ◽  
Vol 36 (3) ◽  
pp. 372-380 ◽  
Author(s):  
B. N. Mandal ◽  
Sudeshna Banerjea
Keyword(s):  
Reflection Coefficient ◽  
Circular Cylinder ◽  
Cross Section ◽  
Water Waves ◽  
Wave Train ◽  
Integral Theorem ◽  
Water Wave Scattering ◽  
First Order ◽  
Transmission Coefficients ◽  
Surface Water Waves

AbstractThe problem of scattering of surface water waves by a horizontal circular cylinder totally submerged in deep water is well studied in the literature within the framework of linearised theory with the remarkable conclusion that a normally incident wave train experiences no reflection. However, if the cross-section of the cylinder is not circular then it experiences reflection in general. The present paper studies the case when the cylinder is not quite circular and derives expressions for reflection and transmission coefficients correct to order ∈, where ∈ is a measure of small departure of the cylinder cross-section from circularity. A simplified perturbation analysis is employed to derive two independent boundary value problems (BVP) up to first order in ∈. The first BVP corresponds to the problem of water wave scattering by a submerged circular cylinder. The reflection coefficient up to first order and the first order correction to the transmission coefficient arise in the second BVP in a natural way and are obtained by a suitable use of Green' integral theorem without solving the second BVP. Assuming a Fourier expansion of the shape function, these are evaluated approximately. It is noticed that for some particular shapes of the cylinder, these vanish. Also, the numerical results for the transmission coefficients up to first order for a nearly circular cylinder for which the reflection coefficients up to first order vanish, are given in tabular form. It is observed that for many other smooth cylinders, the result for a circular cylinder that the reflection coefficient vanishes, is also approximately valid.

Hexagonal Nested Loop Fractal Antenna for Quad Band Wireless Applications

Frequenz ◽  
2019 ◽  
Vol 73 (3-4) ◽  
pp. 99-108
Author(s):  
Robert Mark ◽  
Nipun Mishra ◽  
Kaushik Mandal ◽  
Partha Pratim Sarkar ◽  
Soma Das
Keyword(s):  
Reflection Coefficient ◽  
Low Cost ◽  
Impedance Matching ◽  
Ground Plane ◽  
Fractal Antenna ◽  
Wireless Applications ◽  
Resonant Modes ◽  
Simulation Results ◽  
Nested Loop ◽  
Good Agreement

Abstract A compact hexagonal nested loop fractal antenna with L shaped slot on the ground plane is presented for multiband applications. In this paper, the effect of fractal iterations and position of L-slot on ground plane are optimized for better performance of the antenna. Multiple hexagon loops excite multiple resonant modes at 1.7, 2.4, 3.1, 4.5 and 6 GHz and an L-shaped slot on the ground plane helps to achieve wide bandwidth response with better impedance matching in the 4.25–6.41 GHz frequency band. An equivalent circuit of the proposed antenna is modelled and the same is verified using ADS. Reflection coefficient and radiation pattern are presented to further confirm the performance of the proposed design for wireless applications. The proposed antenna is fabricated on a low-cost FR4 substrate of dimensions 40×32×1.6 mm3 and measured results show good agreement with simulation results.

scholarly journals A super wideband circular-shaped fractal antenna loaded with concentric hexagonal slots

2018 ◽  
Vol 7 (3.29) ◽  
pp. 211 ◽  
Author(s):  
Srinivasarao Alluri ◽  
Nakkeeran Rangaswamy
Keyword(s):  
Wireless Communications ◽  
Reflection Coefficient ◽  
Input Impedance ◽  
Ground Plane ◽  
Fractal Antenna ◽  
Total Size ◽  
Compact Size ◽  
Peak Gain ◽  
Good Agreement ◽  
Microstrip Feed

This article presents a super wideband (SWB) circular-shaped fourth iterative fractal antenna loaded with concentric hexagonal slots. A tapered microstrip feed and a partial ground plane is used. It has a total size of 40 × 27 × 1.6 mm3. Numerical results of the antenna show that it provides a bandwidth from 1.43 GHz to more than 40 GHz (percentage bandwidth greater than 186%) with a bandwidth ratio of approximately greater than 28:1 for S11 < -10 dB. A prototype of the proposed antenna has been fabricated and its performances are measured up to 15 GHz. A good agreement is achieved between the numerical and experimental reflection coefficient, VSWR and input impedance. Measured radiation patterns at different frequencies and simulated peak gain are presented and discussed. It has the advantages of super wide bandwidth and compact size. The developed antenna is suitable for various wireless communications such as GPS, GSM, UMTS, ISM and UWB.  

scholarly journals A Microstrip Second-Iteration Square Koch Dipole Antenna for TT&C Downlink Applications in Small Satellites

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Jorge Simón ◽  
José Luis Alvarez-Flores ◽  
Juvenal Villanueva-Maldonado ◽  
Víctor Hugo Castillo-Topete ◽  
Leonel Soriano-Equigua ◽  
...  
Keyword(s):  
Reflection Coefficient ◽  
Resonance Frequency ◽  
Dipole Antenna ◽  
Fractal Antenna ◽  
Small Satellite ◽  
Maximum Gain ◽  
Small Satellites ◽  
Average Maximum ◽  
Satellite Applications ◽  
Impedance Magnitude

A microstrip second-iteration square Koch dipole fractal antenna is presented. This meandered antenna has a total length of 56.56 cm including its feed gap and was printed on the diagonal of a 100 mm × 100 mm PCB card that acts as CubeSat face. The antenna that was designed to optimize space shows acceptable performance at its resonance frequency of 455 MHz within the 70-centimeter band, a band that is commonly used for TTC CubeSat subsystems. The designed fractal antenna shows a reflection coefficient below −20 dB, a VSWR below 1.2, a −10 dB bandwidth of 50 MHz, and impedance magnitude of 56 Ω, while the average maximum gain around its resonance frequency is 2.14 dBi. All these parameters make this designed antenna suitable for small satellite applications at a band where a linear λ/2 dipolar antenna working at 455 MHz would be about 32.97 cm long, which does not fit within the largest dimension of a CubeSat face corresponding to 14.14 cm.

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